The present invention relates to gyratory crushers in general and, more particularly, to a gyratory crusher of the type which is designed to be a secondary or tertiary crusher in the size reduction of material being removed from a quarry or mine.
Gyrator crushers typically include a rotary means or eccentric mounted by means of bearings on the frame and in some cases, on a main shaft of the frame. A crushing head is mounted by means of bearings on the eccentric at an angle to the frame. The eccentric is rotated through a drive shaft and gearing and as it rotates relative to the frame, the head of the crusher moves alternately toward and away from the bowl of the crusher in a gyratory manner. As material to be crushed moves through the crushing chamber, it is repeatedly subjected to compressive forces and reduced in particle size. Typically, there is a certain amount of drag in the bearings between the eccentric and the crushing head so that the crushing head not only gyrates but also rotates uninhibited about its own axis at less than 15% of the number of gyrations per minute during the crushing operation. Many crushers prior to the present invention provided some means for preventing rotation of the head or at least reducing the speed or rotation of the head during crushing operations; See U.S. Pat. No. 3,908,912 and the anti-spin mechanism in various other patents.
It is the general object of a rock crusher to reduce the size of the material being supplied to the crushing chamber at as rapid a rate as is practical with the smallest machine practical. Conventionally, material moves through the crushing chamber by the force of gravity and a small amount of movement added to the material by the oscillations of the crushing head. As a result, the material movement through the crusher is generally slow and the material is often subjected to a greater number of compressions than is actually necessary to reduce the size of the material to the desired fineness. As a result, in many instances, more "fines" are produced than is desired. These fines must be screened off in order to achieve the desired product size range. In order to move sufficient material through the crusher to achieve the desired capacity, it has heretofore been necessary to have a large machine.
In order to increase crusher capacity, it would be desirable to arrive at a means and method for moving a greater volume of material through the crusher while still being able to subject this material to sufficient number of impacts or compressions to achieve the desired size reduction. Conventionally, this is done by providing a larger machine or operating a machine at a faster speed.
In an effort to increase the amount of material which can be passed through a gyratory crusher and still achieve the desired size reduction, it has been proposed to rotate the bowl of the crusher relative to the crushing head as shown in U.S.S.R. Author's Certificate No. 579011, published Nov. 5, 1977. According to this publication, centrifugal forces contribute to push material towards the discharge opening of the crusher.
By imparting a centrifugal force to the material being crushed, a generally horizontal force is imparted to the particles of material. Gravitational force imparts a vertical force to the material being crushed. If the centrifugal force imparted to the material can be controlled, then the vector sum of the combined gravitational and centrifugal forces acting on a particle of material within the crushing chamber at any given point can be controlled. The vector sum is such that the material is moved through the crushing chamber at a greater speed. The crushing chamber can then be designed so it generally conforms with the trajectory of material moving through chamber. This means that the crushing chamber can be designed so that the material moves through the crushing chamber at a speed which, when coordinated with movement of the crushing head permits a greater volume of material to be passed through the crusher while achieving the desired size reduction but without compressing the material so many times that additional fines are produced. By being able to move material through the crushing chamber at a faster rate, a given size machine can produce a greater volume of product. In addition, a trajectory path formed by the compression members (head and bowl) which is closely related to the vector sum of the gravitational and centrifugal forces reduces the per ton wear rate of the crushing members.
In order to achieve this desired combination of circumstances, it has been found by the present invention that the means for producing an oscillating motion in the crushing head to thereby subject the material to compressive crushing forces should be capable of being independent of the means for imparting centrifugal force to the material being crushed. This allows a control over each of the functions. The centrifugal force imparted to the material within the crushing chamber can be carried out by positively rotating either the crushing head independently of the gyratory motion induced in the crushing head or by independently rotating the bowl of the crusher, or by rotating both. It has also been found by the present invention that it is only necessary to rotate one of the crushing members, i.e., either the crushing head or the bowl of the cruhser and allow the other curshing member to freely rotate. The material within the crushing chamber thereby acts as a clutch between the two crushing members so that both are positively rotated. It should be noted that both crushing members could be rotated and still be within the concepts of the present invention.